Abstract
Patient-derived explant (PDE) culture of solid tumors is increasingly being applied to preclinical evaluation of novel therapeutics and for biomarker discovery. In this technique, treatments are added to culture medium and penetrate the tissue via a gelatin sponge scaffold. However, the penetration profile and final concentrations of small molecule drugs achieved have not been determined to date. Here, we determined the extent of absorption of the clinical androgen receptor antagonist, enzalutamide, into prostate PDEs, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and matrix-assisted laser/desorption ionisation (MALDI) mass spectrometry imaging (MSI). In a cohort of 11 PDE tissues from eight individual patients, LC-MS/MS quantification of PDE homogenates confirmed enzalutamide (10 µM) uptake by all PDEs, which reached maximal average tissue concentration of 0.24–0.50 ng/µg protein after 48 h culture. Time dependent uptake of enzalutamide (50 µM) in PDEs was visualized using MALDI MSI over 24–48 h, with complete penetration throughout tissues evident by 6 h of culture. Drug signal intensity was not homogeneous throughout the tissues but had areas of markedly high signal that corresponded to drug target (androgen receptor)-rich epithelial regions of tissue. In conclusion, application of MS-based drug quantification and visualization in PDEs, and potentially other 3-dimensional model systems, can provide a more robust basis for experimental study design and interpretation of pharmacodynamic data.
Highlights
Www.nature.com/scientificreports the penetration of small molecule agents into the tissue structure, and the in-tissue drug concentrations achieved during culture
Enzalutamide is detectable in Patient-Derived Explant (PDE) culture systems
Validated according to US FDA guidelines, a quantitative LC-MS/MS assay capable of measuring enzalutamide levels in both culture media and tissue specimens from our widely used Patient-derived explant (PDE) model system[26,27] (Fig. 1)
Summary
Www.nature.com/scientificreports the penetration of small molecule agents into the tissue structure, and the in-tissue drug concentrations achieved during culture. Orthodox quantification assays typically involve homogenization of the drug-containing tissue or biofluid, sample clean-up, and separation by liquid chromatography followed by absolute quantification using tandem mass spectrometry (LC-MS/MS). Such approaches yield accurate quantification data, homogenization of tissue samples results in complete loss of spatial information and all measurements represent integrated values for the whole tissue, thereby making it impossible to know whether the molecule of interest is evenly distributed or differentially bio-accumulated, dependent on cell type and tissue penetration. With the advent of mass spectrometry imaging (MSI), it is possible to retain spatial information, allowing detailed mapping of the tissue distribution of molecules of interest such as drugs, metabolites or endogenous compounds such as phospholipids[14,15,16]. We describe the spatial localization of enzalutamide-derived ion signals in tissues with heterogenous histological features and in comparison to immunohistochemical staining of the intracellular drug target, AR
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